Generally the recommended process for a 'washable' print is to print, peel off the paper back, let sit for 24 hours, rinse in cool water, lay flat to dry, then heat set with an iron on a setting suitable for the fabric.

Essentially you have already heat set your piece by fusing, now you can hand wash the garment or machine wash on a gentle cycle in cold water.

The Inkjet fabric sheets are best for applications that will get only light use--they are not the best choice for something like soccer team shirts for example:)